Mi furnace is blowing cool air. The model number is GMP100-3 SERIAL NUMBER IS 9308025348 it sounds like the motor for the flue kicks in but there is no ignition and no flames coming up. So start to blow cool air. The furnace was put in 1993, is it to old? Do we need a new one? My husband took the motor out and he discovered that when the flue motor doesn’t spin but it makes the sound like it wants to start.

My husband took the motor out and he discovered that when the flue motor doesn't spin but it makes the sound like it wants to start.

That is a dangerous situation. Call for oN site professional help.